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Climate Q&A

Are the ozone hole and global warming related?

The ozone hole and global warming are not the same thing, and neither is the main cause of the other.

The ozone hole is an area in the stratosphere above Antarctica where chlorine and bromine gases from human-produced chlorofluorocarbons (CFCs) and halons have destroyed ozone molecules.

Global warming is the rise in average global surface temperature caused primarily by the build-up of human-produced greenhouses gases, mostly carbon dioxide and methane, which trap heat in the lower levels of the atmosphere.

There are some connections between the two phenomena.

For example, the CFCs that destroy ozone are also potent greenhouse gases, though they are present in such small concentrations in the atmosphere (several hundred parts per trillion, compared to several hundred parts per million for carbon dioxide) that they are considered a minor player in greenhouse warming. CFCs account for about 13% of the total energy absorbed by human-produced greenhouse gases.

The ozone hole itself has a minor cooling effect (about 2 percent of the warming effect of greenhouses gases) because ozone in the stratosphere absorbs heat radiated to space by gases in a lower layer of Earth’s atmosphere (the upper troposphere). The loss of ozone means slightly more heat can escape into space from that region.

Global warming is also predicted to have a modest impact on the Antarctic ozone hole. The chlorine gases in the lower stratosphere interact with tiny cloud particles that form at extremely cold temperatures — below -80 degrees Celsius (-112 degrees Fahrenheit). While greenhouse gases absorb heat at a relatively low altitudes and warm the surface, they actually cool the stratosphere. Near the South Pole, this cooling of the stratosphere results in an increase in polar stratospheric clouds, increasing the efficiency of chlorine release into reactive forms that can rapidly deplete ozone.

This entry was posted
on Tuesday, September 14th, 2010 at 4:44 pm
and is filed under Climate: Greenhouse Gases, Global Warming.
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